U.S. President Barack Obama pledged on May 14 to stand by Persian Gulf allies, defending them against external attacks and helping them deal with "destabilizing activities" by Iran in the region.

After a summit with the six Arab state members of the Gulf Cooperation Council at the Camp David presidential retreat, Obama used strong words to allay worries in the Gulf about Iran's growing influence and proxy wars in Syria, Yemen, Iraq, and elsewhere.

"I am reaffirming our ironclad commitment to the security of our Gulf partners," Obama told a news conference at the retreat in the Maryland mountains outside Washington at the end of the summit.

"Let me underscore, the United States keeps our commitments," he said.

Obama also went out of his way to reassure the Gulf monarches that any agreement world powers reach with Iran to limit its nuclear ambitions will be a benefit to the region rather than a threat.

He stopped short of offering a formal defense treaty that some Gulf countries had sought, however, and instead announced more modest measures, including helping them to integrate missile-defense systems, streamlining weapons sales, and increasing military training.

The summit came as Iran raised eyebrows once again on May 14 by firing on a commercial vessel, the MT Alpine Eternity, as it passed through the Gulf -- its second such move in a month.

As in the previous incident in April, Iran cited a financial dispute as the reason for the action. In the first incident, it detained the vessel for weeks at an Iranian port before allowing it to proceed.

Ben Rhodes, Obama's deputy national security adviser, called the MT Alpine incident "exactly the type of challenge" the Gulf nations are focused on, though he added that it was not specifically discussed during the daylong meeting at Camp David.

"The Iranians should not be allowed to get away with it," said Saudi Foreign Minister Adel al-Jubeir. "For whatever reason they're doing it, it's got to stop."

On the key issue of the nuclear deal world powers are negotiating with Iran, Jubeir said Arab leaders were "assured that the objective is to deny Iran the ability to obtain a nuclear weapon" and that all pathways to such a weapon would be cut off.

But he said it was too early to know if a final nuclear agreement would be acceptable.

"We don't know if the Iranians will accept the terms they need to accept," he said.

Obama noted in his press conference that "most of the destabilizing activity that Iran engages in is low-tech, low-cost activity" which would not be particularly enhanced if economic sanctions on Tehran are lifted in exchange for limits on its nuclear activities -- a key fear Arab states have voiced.

While much of the focus of the summit was on Arab concerns over Iran, Obama said their intent is not to "marginalize" Iran.

"The purpose of security cooperation is not to perpetuate any long-term confrontation with Iran or even to marginalize Iran," he said, adding he hopes the region achieves "the kind of peace and good neighborliness with Iran that I think so many of the countries here seek."